This invention relates to an anti-jackknifing apparatus for a semitrailer rig.
Such an anti-jackknifing apparatus is known from U.S. Pat. No. 4,109,929. As disclosed in that patent, a wedge on a trailer is inserted into a fifth wheel on a tractor and is extended rearwardly, whereby the wedge can cooperate with a brake disk disposed on the trailer and circularly surrounding the fifth wheel. Upon a braking of the tractor during linear or straight forward motion, a rear part of the wedge is simultaneously pressed against the brake disk, thereby preventing a shearing out of the trailer relative to the tractor. When the semitrailer rig is traveling through a curve, the pressure of the wedge against the brake disk is weaker. The wedge and brake disk assembly, therefore, operates independently of the speed of the semitrailer rig. Moreover, when the rig is maneuvered at lower speeds, there exists an undesirable braking of the trailer.
Further devices are known, which effectuate an attenuation of the rotary movement between the tractor and the trailer (attenuation of the jackknifing angle) either as a function of the speed of travel only or as a function of the brake pressure only.
Thus, as disclosed in German Offenlegungschrift No. 30 04 409, an anti-jackknifing apparatus comprises two pairs of single-action hydraulic cylinders cooperating with a hydraulic valve group and a control unit to attenuate the angular movement between tractor and trailer more or less strongly as a function of the vehicle speed. In addition, U.S. Pat. No. 4,015,856 describes a stabilization device for controlling the swinging of a trailer where two single-action hydraulic cylinders bring about an attenuation of jackknifing angle in connection with a pin and a cable placed around the pin and connected with the tractor.
Lastly, from U.S. Pat. No. 3,250,547 a hydraulic control system for semitrailer rigs is known where unimpeded maneuvering of a semitrailer rig with unattenuated jackknifing of the trailer is made possible by opening a valve.
An object of the present invention to provide an improved anti-jackknifing apparatus of the above-mentioned kind.